Ion accelerators with closed electron drift, also known as “Half effect thrusters” (HETs), have been used for spacecraft propulsion. Representative applications are: (1) orbit changes of spacecraft from one altitude or inclination to another; (2) atmospheric drag compensation; and (3) “stationkeeping” where propulsion is used to counteract the natural drift of orbital position due to the effects such as solar wind and the passage of the moon. HETs generate thrust by supplying a propellant gas to an annular gas discharge channel. The discharge channel has a closed end or base which typically includes an anode, and an open end through which the gas is discharged. Free electrons are introduced into the area of the exit end from a cathode. The electrons are induced to drift circumferentially in the annular exit area by a generally radially extending magnetic field in combination with a longitudinal electric field, but electrons eventually migrate toward the anode. In the area of the exit end, a goal is to achieve collisions between the circumferentially drifting electrons and the propellant gas atoms, creating ions which are accelerated outward due to the longitudinal electric field. Reaction force is thereby generated to propel the spacecraft.